Speed limiting control for gas turbines



July 17, 1956 w. F. EHORN 2,754,657

SPEED LIMITING CONTROL FOR GAS TURBINES Filed May 17, 1951 William l? Ehorr,

E His Attorneg.

United States Patent SPEED LIMITING CONTROL FOR GAS TURBINES William F. Ehorn, Middletown, Ohio, assignor to General Electric Company, a corporation of New York Application May 17, 1951, Serial No. 226,906

7 Claims. (Cl. Gil-39.14)

This invention relates to uid pressure turbines and particularly to speed limiting arrangements for turbine type starter motors for internal combustion power plants.

The invention may be used with turbine type starter motors for gas turbine power plants and also for starting reciprocating engines since either of these types of power plants have moving parts of considerable mass and thus require the expenditure of substantial amounts of energy in order to effect starting. If, during the starting operation, the starter becomes disconnected from its load, as for example, due to the power plant accelerating under its own power rather early in the starting cycle, or due to failure of the driving mechanism, it is necessary to provide quick acting means for preventing over speeding of the turbine type starter to a dangerous degree. In practice, this is a very diflicult problem to solve in view of the fact that the physical proportions of the turbine type starter are usually such that its rotating parts have very little inertia. Furthermore, it is generally impractical to provide these rotating parts of the starter with sufficient inertia to prevent overspeeding of the starter, particularly in the case of aircraft applications, since this would require more space and weight than is usually permissible. Furthermore, with increased inertia in the starting motor, the energy available for starting a given power plant would be greatly reduced because a larger portion of this energy would be required merely to accelerate the increased mass of the starter rotor. Therefore, it will be apparent that any device employed to prevent overspeeding of such a turbine type starter must be capable of acting within a very short time interval in view of the relatively low inertia of the rotating parts of the starter motor. Accord ingly, it is an object of this invention to provide an improved fuel feeding system which obviates the abovementioned difficulties. f

Another object of the invention is to provide an improved fuel feeding system which will prevent turbine type starting motors from reaching an unsafe speed, and which is mechanically simple, quick acting, and light in weight.

A further object of the invention is to provide an improved fuel feeding system in which protection is provided against excessive amounts of fuel being supplied to a turbine type starter motor.

Still another object of the invention is in the provision of an arrangement wherein a turbine type starter is automatically disconnected from a prime mover and the energy supplied to the starting turbine is interrupted if there is a tendency for power to be delivered from the prime mover to the starter. Other objects and advantages will be apparent from the following description taken in connection with the accompanying drawing, lin which the single figure is a diagrammatic representation of a turbine type starter motor provided with a fuel feeding system in accordance with the invention.

Referring to the drawing, a gas turbine type starter is indicated generally at 1. The starter comprises a turbine section 2, a combustion chamber 3, and a clutch portion 4. If desired, the turbine starter may be arranged to be supported by the engine that it is to start with the provision of a mounting flange S. The turbine delivers power through reduction gearing (not shown) to the clutch 4 which is of the overriding or unidirectional type. The driven side of the clutch is attached to a shaft member 6. Shaft member 6 is provided with a splined portion 6a for engaging an engine member (not shown) in driving relation.

The term overriding or unidirectional clutch means as used herein, is intended to mean any type of clutch structure for the transmission of power in one direction only. For example, clutch means 4 is intended to transmit power from the turbine 2 to the driven member 6 which in turn will drive an engine to which the starter is connected, but will not permit the transfer of power from the engine through shaft member 6 to turbine 2. This is accomplished in accordance with the invention by the provision of a pressure actuated jaw type of clutch connected in the manner to be described hereinafter, or, by the provision of a well-known pawl type or sprag type of clutch means. The details of a clutch of the pressure actuated type are described with greater particularity in Patent 2,488,540-Hollingsworth, and a clutch of the sprag type is described with greater particularity in Patent 2,473,250-Hofman.

Motive fluid for driving the turbine is generated in the combustion chamber 3 which delivers combustion products under pressure and at elevated temperatures to the turbine portion 2. The combustion products are generated by burning fuel which has been mixed with a combustion supporting fluid suchas air or oxygen. The air or other combustion supporting uid may be supplied by a storage bottle 7 of a well-known type used for the storage of air, oxygen, nitrogen, acetylene, or other fluids under high pressures. Communication is established between the fluid supply bottle 7 and combustion chamber 3 by the provision of conduits 8, 8a.

The fluid storage bottle 7 can be of any practical size and yits pressure level need not be fixed to any particular pressure value. Size and weight considerations and availability of bottles will determine the precise pressure level to be used. However, since fluid supply bottles of the type described are presently available for use at pressure levels of the order of three thousand pounds per square inch, the fuel feeding system and its associated controls are illustrated for use at such a pressure level. It is to be understood, however, that the invention is not limited thereto, and that the invention can be used at any desired pressure level. g

Control over the operation of the turbine type starter 1 is accomplished by the provision of a shut off valve 9 connected in series flow relation with conduit 8. As illustrated, shut olf valve 9 is of a well-known type including a solenoid 10 to open the valve in response to an electrical voltage which may be applied to the solenoid and also including means biasing the valve to closed position when no voltage is applied to solenoid 10. Additional control means 11 are also connected in series ow relation with conduit 8 and shut oif valve 9 at the downstream side thereof for reducing the pressure of the Huid supplied to combustion chamber 3. As illustrated in the drawings, the additional control means 11 is a constant pressure regulator which may be of any well-known type arranged to maintain the pressure at the downstream side of regulator '11 at a constant value irrespective of varia` tions in the uid supply pressure of bottle 7. It will be recognized that the supply pressure within bottle 7 will vary over a considerable range as fluid is drawn from the bottle. However, the invention is not limited to the use of regulating means 11 of the precise type described.

At the downstream side of regulating means 11, a pressure relief valve 12 is provided to prevent excessive pressures from being attained in the fuel feeding system at locations downstream from the pressure relief valve.

ln order to provide means for supplying fuel under pressure to the combustion chamber 3, a fuel chamber device 13 is provided. The fuel'cliamber device 'is'essentially a well-known 'type of fluid accumulator Vcornprising an outercasing 14 havirigfprssuretndfuelports 15, 16 respectively. Outercavsin'g L14-is "divided into ja pressure receiving chamber 17 "and 4fuelfehainb'er 18 which are separated by A'a'c'cbrr'inri'ofn "iieible separating wall 19. Communicationis 'establishedbetween conduit 8 and'chamber 17 bythe provision of 'a branch 'conduit 20 connected toport 15. A one-way.restrictorvalve or shuttle valve 21 is connected in 'iseriesflow relation with branch conduit 20 between 'Acondtlit'rS adp'riessure'port for a purpose to be-eXplai eiilie'r'einaft'en Valve body 22 is provided Lwitha'ce'iitral boe portion 23 within Vwhich yis '-slid'bly ed sed o fprsron v24. `A biasing spring 2'5 is also xj'prc'ivided within bore `portion 23 to urge piston 24 ina'n upward'dii'efction, 'Coaxial with bore portion 23isa second bre'prti'on'2'6`in`which a second piston member 27 is slida'bly disposed. Spac'ed annular recesses 28, "29 aifepi-ovidedatftheisurface of bore portion 26. Recess '29 'communicates v/ 'thjthe 'tmosphere and with the under sideofpisto'n 'Z'tlby'passageways 30, 31, respectively. Recess '28 communicates with the upperside 'oftpiston 24b'y connecting passageway 32. A'passageway '33 'extendsdiam'etric'ally across smaller piston 27 and an axially extending l'passa'geway 34 establishes communication between the'lower end of piston 27 and passageway 33. The upper lportion 'f bore 23 communicates with 'an in'le'tport'BS V'an'd't'lie lower portion of bore26 communicates withanou'tlet'p'ort36.

Passageway 33 is spacedfrorn'tlie lower end` portion of piston 27 by an amount crespordingto the spacing between recesses 28,29. Likewise,the"'lo'cation at which passageway 32 communicates with lthe'bore portion23 is spaced in relation `to'"reces"ses 28, A2'9 so Athat piston 24 will isolate passageway when `-pi's'ton '2`4 is"moved upward by an amount suliicint'to'estzblish communication between outlet port'li'an'd theitmosplere through passageways 30, 33, and 34.

When r'nain control` valve' 9 isopen4 so that Jfluid pressure is admittedto'bore'portion 2A3Wthrough conduits'S, 20, the pressure acting against the upper face of piston 24 forces it downward against the action ofbiasing-spring 25 until piston 24 'and piston 27 assume theposition indicated in the drawing. AIn suchpositio'n, it willfbeapparent that valve 21 is open inthe sense lthata restricted passageway is provided toadniit'uidto chamberl 17,7the restricted passageway being completed from inlet .port 35, through bore portion 23,-*passageways 'S2- 34,-bore portion 26, to discharge'port 36. During normal'operation, there is no ow of fluid through conduit and restrictor valve 21. Theo pressure acting fagainst the upper face of piston24 alsoaets in the opposite sense against the face of piston 27. IHowever, sinceA piston127 is of considerably smaller'crosssectional areal than that of piston 24, there is always'suicientnforce acting against piston 24 in a downward direction to cause piston`24 and piston 27 to move 'downward against the action vof biasing spring'25. lffor any reason there is a tendency for a reverse iiow of fluid to occur from chamber-17 upward through valve'21 toward pressure regulator 1 1 and relief valve 12, the pressure inj bore portion 26 will be greater than the pressureacting against-piston24, at least momentarily. It will 'be apparent to Vthose skilledin the art-that, because of thefa'ct that passageways- 32-34 are restricted as compared to Vconduit-Baland the ilow areas provided incombustion chamber Sand turbine 2, the pressure in conduitSa will drop a tafaster rate than the rate of `pressured'rop in' chamber -17 after valve 9 is closed. kMomentarily, therefore, --th'e pressure in chamber Y17 will exceed the pressureacting='against the upper face of pistonl24.

accumulator 413 vserves a triple purpose.

An important feature of my invention is that the fluid First, it provides a means for receiving fuel into the fuel feeding system, secondly, it serves as a metering device in that only a definite pre-established quantity of fuel can be supplied to the combustion chambers each time the turbine starter is operated, and thirdly, in combination with the connection to storage 'bottle 7 it provides a means for supplying fuel under pressure tothe combustion chamber 3. The fuel is conveyed from chamber 18 to combustion chamber S'by conduit 37. A check valve 38 is connected in series flow relation with conduit 37 to preventflow 'fromcombustion chamber 3 to'fuelchamber 18.

While a particulartyp'eof iiuidfaccumulator has been illustrated and described it will be understood that the invention is not necessarily limited theretto and that other types of accumulators may be employed with equally good results.

`lf apressure actuated clutch of the type described in the kabove mentioned Hollingsworth 'patent is employed, a branch conduit 8b is provided 'to supply vfluid under pressure tothe clutch. Conduit`8b is connected to conduit `8 at 'anydesired locationon the downstream 'side'of control valve 9. LIn this way, clutch 4 will'b'e actuated tofengage shaft6 in driving relation'when Huid under pressureis being'suppliedto combustion chamber-3. At the same time, such anarrangement provides an automatic safety feature in that'the clutch 4 will vnot engage shaft in driving relation when nofluid'is'b'eing supplied to combustion chamber 3.

lf 'a unidirectional 'clutch of the pawl o r spragtype is employed, conduit t'b'is omitted. `When either "inc pawl or'the spra'g type 'of clutchis employed, there can 'befno transfer of power from shaftl to th'e'turbinepoit'ion V2 under 'any'normal operating condition, but 'po'wer'can be transmitted in the opposite direction .from turbine 2'to shaft' 6. y

'Another safety feature is in the provision of 'means'.fo'r preventing dangerous overspeeding of the turbine`2. xThis is accomplished in 'accordance vwith 'the inventionby the provision' of a switch 39. Switch '39 is of 'a well-known type which -is'n'ormally closed and Vwhichlis operable 'in responseto 'rotationalspeed of 'the turbine 2 to 'open switch contacts 40, '41 when the operating 'speedof' the turbine reachesa preselected value. In'order to .provide manual control'over the operation 4of 'the turbinetype starter 1, manually operable switches' 42, '43 arel provided. Switches 3 9, 42, '43, 'and Vsolenoid j10"are connected 'in series electrically to 'terminals 44, ``45"which are adapted to receive anelectrical voltage. The"rneansfor supplying voltageV to'te'rrninals 44 and `45"forms no part of the present invention, but for the purposes *ofillust'ration is shown 'as'b'at'tery 46.

lSwitches 39 'and 42 are 'of'thenorrrially closed type. Switch "43 is' 'of the normally' open type-and, in addition, is of"the"'type 'having ai'holding coil 47 for maintaining the switch in the closed position once it hasl beenfactuated by the operator. In addition, switch 43 isof the type having spring '48 biasing switch 43 'to'its open position, and switch 42 is of the type having` a spring 49v biasing switch 4 2 to its closed position.

4Assuming lthatmfluid supply bottle `7 'has' been charged with combustion supporting uidand that a charge of fluid fuel has' been placed in fuel chamber`518, in .order to put 'the' fuel feeding system into operation, vthe operator manually closesswitch 43. 'Sincethislswit'ch isprovidd withholding "coil47 the'volta'gec's'pplied to terminalsA 44, 451energizescoil"47'and solenoid '1Q so that switch '-43 remains fin its 'closed' position 'and' main control 'valve 9 is -caused' to Iopen and remain' 7open by' vir'tue lof'v solenoid 10 "being energized. @ombustion supporting `iiuid' Eflows from supply .b'ot-tle7througn 'Conduits'8,-`3a, 1ir'xain'fcont'rol valve'9,iand 'regulating'meanslIfto-Yconibustion chamber .3, f-TSince thenuidecemuiator' 13-.iseonneeted 'tocodu'it chamber 17 thereby causing the fuel charge in chamber' 18 to be forced through check valve 38 and conduit 37 to combustion chamber 3. The combustion supporting Huid from conduit 8 and the fuel from conduit 37 are mixed and burned in combustion chamber 3 to provide motive fluid for driving the turbine 2. When main control valve 9 is in the open position, liuid under pressure is supplied to pressure actuated clutch 4 through conduit 8b so that turbine 2 and shaft 6 are connected in driving relation. If a clutch of the pawl or sprag type is employed, turbine 2 and shaft 6 will be connected in driving relation as long as sufficient energy is being delivered to the turbine so that there is a tendency for energy to be transferred from the turbine 2 to driven shaft 6. If, for any reason, there is a tendency for energy to be transferred in a reverse direction, thatis, from shaft 6 to the turbine portion 2, these elements become disconnected from driving relation and clutch 4 will slip.

In the event that an excess amount of energy is supplied to the turbine for any given operating condition, turbine overspeeding is prevented since speed responsive switch 39 will open contacts 40, 41 and thus deenergize solenoid 10 at some preselected operating speed of the turbine. When solenoid 10 is deenergizred the main control valve 9 will quickly return to its closed position under the influence of its biasing means (not shown). In addition, the operator can discontinue the operation of the starter 1 before turbine 2 has reached any dangerous overspeed condition by merely opening switch 42. By opening switch 42 solenoid 10 and holding coil 47 are deenergized thereby causing main control valve 9 to close under the action of its biasing means, and switch 43 to open and remain open under the action of biasing spring 48.

Under certain operating conditions, there may be a tendency for a backward ow of Huid through conduits 37 and 20. Such backward flow is prevented by check valve 38 and valve 21, respectively. In addition to operating somewhat in the manner of a check valve, the one-way restrictor valve 21 also operates to establish communication between chamber 17 and the atmosphere when uid pressure is removed from the upstream side of the valve. Check valve 38 is of the type wherein the valve is provided with relatively strong biasing means urging the valve to its closed position so as to prevent fuel in chamber 18, conduit 5l at the downstream side of valve 52, and in conduit 37 between valve 38 and port 16 from passing through check valve 3S into chamber 3 due to the weight of such fuel during periods when valve 9 is closed. Such arrangement permits fuel chamber 18 to be filled with a fresh charge from a fuel reservoir 50 through conduit 51 by gravity action by opening valve 52 during periods when the starter turbine 1 is not in operation thereby avoiding the necessity for heavy, complicated, and expensive high-pressure fuel pumping means. After fuel chamber 18 has been filled, valve 52 is again closed so that only a metered amount of fuel is admitted to the starter turbine during its operation.

While a particular embodiment of the invention has been illustrated and described it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention, and it is intended to cover in the appended claims all such changes and modifications that come within the true spirit and scope of the invention.

What i claim as new and desire to secure by Letters Patent of the United States is:

l. In a fluid feeding system, the combination comprising means for supplying iluid under pressure, a turbine power plant including a combustion chamber and a turbine, a pair of terminals adapted to receive electrical voltage, normally closed speed responsive switch means including means rotated by said turbine and operable to open at a preselected operating speed of said turbine,

first conduit means including normally closed electrically actuated valve means connecting said supply means to said combustion chamber, means including normally open switch means for energizing said valve means, and means connecting the normally open and the normally closed switch means and said valve means electrically in series with said terminals, whereby said speed responsive switch means open at said preselected operating speed of said turbine to de-energize said valve means and interrupt the supply of liuid in the combustion chamber, and clutch means included in said turbine, said clutch means operable in response to liuid pressure to engage a member in driving relation, and second conduit means connecting said clutch means to the first conduit means at a location between said valve means and said combustion chamber, whereby said clutch is engaged when iiuid is being supplied to the combustion chamber and is disengaged when the supply of fluid is interrupted.

2. In a fluid feeding system, the combination comprising means for supplying liuid under pressure, a turbine power plant including a combustion chamber and a turbine, a pair of terminals adapted to receive an electrical voltage, normally closed speed responsive switch means including means rotated by said turbine operable to open at a preselected operating speed of said turbine, conduit means including normally closed electrically actuated valve means connecting said supply means to said cornbustion chamber, means including normally open switch means for energizing said valve means, and means connecting the normally open and the normally closed switch means and said valve means electrically in series with said terminals, whereby said speed responsive switch means opens at said preselected operating speed of said turbine to de-energize said valve means and interrupt the supply of fluid to the combustion chamer, an accumulater having a pressure receiving chamber and a fuel chamber with a movable wall between said chambers, second conduit means connecting the fuel chamber to the cornbustion chamber, means for supplying fuel to said fuel chamber, and third conduit means connecting the pressure receiving chamber to the rst conduit means at the downstream side of the electrically actuated valve means.

3. In a iluid feeding system, the combination comprising means for supplying combustion supporting fluid under pressure, a turbine power plant including a combustion chamber and a turbine having clutch means operable in response to liuid pressure to engage a member in driving relation, first conduit means including normally closed voltage responsive valve means connecting said supply means to said combustion chamber, an accumulator having a pressure receiving chamber and a fuel chamber with a movable wall between said chambers, second conduit means connecting the fuel chamber to the combustion chamber, means for supplying a preselected amount of fuel to the fuel chamber, third conduit means connecting the pressure receiving chamber to the rst conduit means at a location between said valve means and said combustion chamber, fourth conduit means connecting said clutch means to the rst conduit means at a location between said valve means and said combustion chamber, a pair of terminals adapted to receive an electrical voltage, normally closed speed responsive switch means operable to open at a preselected operating speed of said turbine, means including normally open switch means for energizing the valve means, and means electrically connecting said valve means and said switch means in series with said terminals, whereby fluid under pressure and a preselected amount of fuel are supplied to the combustion chamber and the clutch means is engaged when said valve means is energized and the supply of fluid is interrupted and the clutch is disengaged at a preselected operating speed of the turbine.

4. A fuel feeding system comprising means for supplying combustion supporting fluid under pressure, walls defining a combustion chamber, first conduit means including a valve connecting said supply means to said 7 reaction chamber, -an accumulator having a pressure chamber and afuelcharnber witharnovablewall therebetweenand havinga pressure port communicating with the pressure chamber and a fuel portcommunicating with the fuel chamber, secondconduit means connecting said fuel port tosaid combustion chamber, accumulator discharging means including thirdconduit means-connecting said-,pressure port-to said first conduit means at the downstream side of said valve, and means -for `charging said fuel chamber with a predeterminsdquant'ity of a second uid when saidvalve is in a `closed position whereby fuel and combustion supporting fluids are supplied to` lsaid combustion chamber lwhen said valve is in an opengposition,

5. Apparatus in accordance with claim 4 whereinsaid third conduit means includes means establishing communication between said pressure port and the first conduif means at a location betweenrsaidcombustion chamber and said valve when the pressure at said location is Yat least equal to the pressureinisaid third .conduit means and for interrupting said communicationand establishing communication between said pressureaport and the atmosphere when the pressure -at said pressure port exceeds the pressure in said rstconduit'rneans.

6. A fluid feeding systemrcomprising means for supplying a first fiuid under pressure, wallsdefining a first chamber wherein said first fluid chemically unites with asecond fiuid in an exothermal reaction, first `conduit means including a valve connecting said supply means to saidfirst chamber, an accumulator havingl a second chamber and a third chamber With a movable wall therebetween andhaving a pressure port communicating lwith said secnd chamber, and a second port communicating with said third chamber,.second conduitmeansconnecting said second Apor-t to said first chamber, accumulator discharging means :including `third conduit means connecting said pressure port to .said first conduit means at :the downstream side ofsaid valve and means for .charging said thirdchambervwth apredetermined 4quantity of said second 'fluid when -said valve is in a closed position whereby said firstand second fluids are supplied-'to said first chamber-whensaidvalve is in an open position.

7. 4Apparatus rinaccordance with claim 6 wherein said third conduit means includes means establishing communication-between saidzpressure port and the first conduit means at ailocation-between said first chamber and said valve -when'the v.pressure at said location is at least cqua11to thetpressure .in said third conduit means and for interrupting said communication and establishing communicat'ion between :said pressure port and the atmosphere when the pressureiat said pressureport exceeds the pressure in said first conduit means.

References 'Cited in the file of this patent UNITED STATES ."PATENTS 641,117 Kaye 1311.9, 1900 '2,227,666 Noack Jan. 7, 1941 2,411,552 New Nov. 26, 1946 v2,443,648 Austin June 22, 1948 2,540,991 Price Feb. 6, 1951 2,547,660 Prince Apr. 3, 1951 2,559,006 Clapham June 3, 1951 FOREIGN PATENTS 616,695 vGreat'Britain Ian. 26, 1949 

